2nd Gear Starts - Random

[JorgeS]

My 2005 Yukon has ~145,000 miles.
Very little towing; I bought it with 103,000 and it had never had a trailer hitch installed. Transmission fluid was clearly changed before I bought it, and it is still a bright pink color. I installed a Curt hitch and have done some light towing with it, but nothing big.
Here's the issue: Every once in a while, after coming to a stop, it will start in 2nd gear, then quickly shift to 1st. This happens VERY quickly, as in less than one second after you press the accelerator, it will start to move, then shift down; you can feel the jump in torque when this happens, then everything is OK...until the next time it does it.
It happens very irregularly, maybe every few weeks, there may be a couple of months between incidents. I have not noticed any pattern leading up to this.
Anyone else experienced the same thing?

I do plan on putting in a Corvette servo and replacing the TC clutch solenoid with a solid spool to maintain TC lock-up while driving.

Thanks!

 

[stutaeng]

I'm not familiar with the 4L60e, but recommend that you look into the troubleshooting diagnostics on the ATSG manual. Here's a PDF copy of it: https://atoc.ru/uploads/manual/5fb797a513efb.pdf

Is this your symptom?



Doubt a sprag was installed backwards, but it may be failing intermittently.

I was rebuilding a 4L80e for my brother's 90 C1500 a few years ago and initially overlooked the direct clutch sprag. It worked well and was at one point playing around with it after my regular cleaning pass, then all of the sudden I was able to freewheel both directions, which is not supposed to happen. I ordered an upgraded, late-production 34 element sprag since that was the early 16 element sprag). When I took apart the old one, the little cage-looking thing that holds the little elements had broken in a few places...

 

[JorgeS]

Wow! that's an awesome document - THANK YOU!

I think it's different. Seems that if the clutch were in backwards, it would always act improperly. As it is, it rarely does it, working perfectly the rest of the time. Even when it does do it, I don't remember it ever doing it more than once in a day, or maybe weeks between incidents.
Really puzzling...

 

[frumpster]

Downshift solenoids ma be getting weak? My 03 Silverado with 4l60 does what you describe,every once and a while,and I suspect soninoid not shifting to 1st when coming to a stop.

 

[JorgeS]

Interesting... does yours seem to do it more frequently with passing time?
Mine does not seem to be getting worse (doing it more frequently), but it is hard to tell. I may try to keep track of when it does it. Last time it was around Jan 4th.
Thank you.

 

[frumpster]

It is my 2nd vehicle.It only sees around 5 k per year. 03 rcsb 4x4. 237 km. Maybe once per year. Can be sitting at light, give her gas,she sorta rolls out slow,then,hits sorta like a neutral drop at 2mph, then shifts fine. Is this what yours is like? Researched it a lot, if I were to drive it more I would take pan off and do the solinoids, fairly cheap,I'm just lazy. Let me know what you think, or do...eh!

 

[JorgeS]

It's never "acted.up" in a spirited start, so.the jump isn't very harsh. Each time it's done it has been on a gentler start, last time my wife was driving and she's typically much gentler than me.
Having said all that, kind of like you describe, feels like a downshift.

 

[AuroraGirl]

My 2005 Yukon has ~145,000 miles.
Very little towing; I bought it with 103,000 and it had never had a trailer hitch installed. Transmission fluid was clearly changed before I bought it, and it is still a bright pink color. I installed a Curt hitch and have done some light towing with it, but nothing big.
Here's the issue: Every once in a while, after coming to a stop, it will start in 2nd gear, then quickly shift to 1st. This happens VERY quickly, as in less than one second after you press the accelerator, it will start to move, then shift down; you can feel the jump in torque when this happens, then everything is OK...until the next time it does it.
It happens very irregularly, maybe every few weeks, there may be a couple of months between incidents. I have not noticed any pattern leading up to this.
Anyone else experienced the same thing?

I do plan on putting in a Corvette servo and replacing the TC clutch solenoid with a solid spool to maintain TC lock-up while driving.

Thanks!

I don’t know what years or applications but some 4l60e I’m pretty sure are normal to start in 2nd gear

 

[stutaeng]

I don’t know what years or applications but some 4l60e I’m pretty sure are normal to start in 2nd gear

Huh?

I had never heard of this before...

Maybe on the tuning tables one can look to see if that's the case? IDK?

 

[JorgeS]

I don’t know what years or applications but some 4l60e I’m pretty sure are normal to start in 2nd gear

That's weird...
I doesn't feel like it's normal. If it was, it would stay in 2nd gear (or whatever gear it starts in). It certainly feels like an anomaly.

 

[AuroraGirl]

It’s not the issue here but I figured to mention it’s a thing that is capable in some applications
1996 Camaro for example

 

[99Sierra2500]

If the MAF hasn't been cleaned in a while, I would do that.

 

[JorgeS]

It’s not the issue here but I figured to mention it’s a thing that is capable in some applications View attachment 5331
1996 Camaro for example

Interesting... pre-electronic transmissions, especially RWD vehicles, this was something one did to try to keep from spinning the wheels. Several of my vehicles had this ability.
Thanks for sharing!

 

[AuroraGirl]

Interesting... pre-electronic transmissions, especially RWD vehicles, this was something one did to try to keep from spinning the wheels. Several of my vehicles had this ability.
Thanks for sharing!

The 4l60e is electronic lol. But yes , prevent from breaking traction in normal driving if the tire and ratios and rear weight were conducive to slipping

 

[JorgeS]

We had a S-10 (4-Cyl, 5-Spd) and the bed-liner had provisions for putting a 2x4 across, behind the wheel wells. We used to put two decent-sized bags of sand (~50 Lbs each) in that spot and it helped greatly; you probably would not want to do that on a Camaro.